Imperial units

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Imperial units
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{{About|the post-1824 measures used in the British Empire and countries in the British sphere of influence|the units used in England before 1824|English units|the system of weight|Avoirdupois system|United States customary units|United States customary units|an overview of UK and US units|Imperial and US customary measurement systems|the political ideology|Imperialism}}{{short description|system of units formerly used in the British Empire and still used in the United Kingdom}}
missing image!
- Weights and Measures office.jpg -
upright=1.2|The former Weights and Measures office in Seven Sisters, London (590 Seven Sisters Road).
The system of imperial units or the imperial system (also known as British ImperialBOOK, Britannica Educational Publishing, The Britannica Guide to Numbers and Measurement,weblink 10 December 2011, 1 August 2010, The Rosen Publishing Group, 978-1-61530-218-5, 241, or Exchequer Standards of 1825) is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced. The imperial units replaced the Winchester Standards, which were in effect from 1588 to 1825.BOOK, Chaney, Henry James, A Practical Treatise on the Standard Weights and Measures in Use in the British Empire with some account of the metric system,weblink 11 September 2016, 1897, Eyre and Spottiswoode, 3, The system came into official use across the British Empire. By the late 20th century, most nations of the former empire had officially adopted the metric system as their main system of measurement, although some imperial units are still used in the United Kingdom, Canada and other countries formerly part of the British Empire. The imperial system developed from what were first known as English units, as did the related system of United States customary units.


The Weights and Measures Act of 1824 was initially scheduled to go into effect on 1 May 1825.BOOK, Great Britain, The statutes of the United Kingdom of Great Britain and Ireland (1807-1865),weblink 31 December 2011, 1824, His Majesty's statute and law printers, 339–354, However, the Weights and Measures Act of 1825 pushed back the date to 1 January 1826.BOOK, Great Britain, William David Evans, William David Evans, Anthony Hammond, Thomas Colpitts Granger, A collection of statutes connected with the general administration of the law: arranged according to the order of subjects,weblink 31 December 2011, 1836, W. H. Bond, 306–27, The 1824 Act allowed the continued use of pre-imperial units provided that they were customary, widely known, and clearly marked with imperial equivalents.

Apothecaries' units

missing image!
- Imperial standards of length 1876 Trafalgar Square.jpg -
Imperial standards of length 1876 in Trafalgar Square, London.
Apothecaries' units are mentioned neither in the act of 1824 nor 1825. At the time, apothecaries' weights and measures were regulated "in England, Wales, and Berwick-upon-Tweed" by the London College of Physicians, and in Ireland by the Dublin College of Physicians. In Scotland, apothecaries' units were unofficially regulated by the Edinburgh College of Physicians. The three colleges published, at infrequent intervals, pharmacopoeiae, the London and Dublin editions having the force of law.BOOK, Edinburgh medical and surgical journal,weblink 29 July 2012, 1824, A. and C. Black, 398, BOOK, Ireland, Butler, James Goddard, Ball, William (barrister.), The Statutes at Large, Passed in the Parliaments Held in Ireland: From the twenty-third year of George the Second, A.D. 1749, to the first year of George the Third, A.D. 1761 inclusive,weblink 29 July 2012, 1765, Boulter Grierson, 852, Imperial apothecaries' measures, based on the imperial pint of 20 fluid ounces, were introduced by the publication of the London Pharmacopoeia of 1836,BOOK, Gray, Samuel Frederick, Samuel Frederick Gray, A supplement to the Pharmacopœia and treatise on pharmacology in general: including not only the drugs and preparations used by practitioners of medicine, but also most of those employed in the chemical arts : together with a collection of the most useful medical formulæ ...,weblink 29 July 2012, 1836, Longman, Rees, Orme, Brown, Green, and Longman, 516, WEB,weblink A Translation of the Pharmacopoeia of the Royal College of Physicians of London, 1836.: With ..., the Edinburgh Pharmacopoeia of 1839,BOOK, The Pharmacopoeia of the Royal College of Physicians of Edinburgh,weblink 29 July 2012, 1839, Adam and Charles Black and Bell and Bradfute, xiii–xiv, and the Dublin Pharmacopoeia of 1850.BOOK, Royal College of Physicians of Dublin, Royal College of Physicians of Ireland, Royal College of Physicians of Ireland, The pharmacopœia of the King and queen's college of physicians in Ireland,weblink 29 July 2012, 1850, Hodges and Smith, xxii, The Medical Act of 1858 transferred to The Crown the right to publish the official pharmacopoeia and to regulate apothecaries' weights and measures.BOOK, Great Britain, A collection of the public general statutes passed in the ... year of the reign of ...,weblink 29 July 2012, 1858, Printed by G. W. Eyre and W. Spottiswoode, Printers to the Queen, 306,



Metric equivalents in this article usually assume the latest official definition. Before this date, the most precise measurement of the imperial Standard Yard was {{val|0.914398415}} metres.Sears et al. 1928. Phil Trans A, 227:281.{{Clear}}{| class="wikitable" cellspacing=4 style="margin-right:0"|+ Table of length equivalent units! Unit! Relative to previous! Feet! Millimetres! Metres! Notes
thou (th)| {{frac12000}}}} 0.0254 {{val|0.0000254}}|
Also 25.4 μm. Also known as milJerrard and McNeill, Dictionary of Scientific Units, second edition, Chapman and Hall; cites first appearance in print in Journal of the Institution of Electrical Engineers (G.B.) vol. 1, page 246 (1872)
inch (in or ″)| 1000 thou {{frac|12}} 25.4 0.0254|
(1 metre = 39.3701 inches)
''Foot (unit)'' (ft or Prime (symbol)>′)| 12 inches 1 304.8 0.3048|
yard (yd)| 3 feet 3 914.4 0.9144|
Defined as exactly 0.9144 metres by the International yard and pound agreement of 1959
chain (ch)| 22 yards 66 {{val|20116.8}} 20.1168|
100 links, 4 rods or {{frac|10}} of a furlong. The distance between the two wickets on a cricket pitch
furlong (fur)| 10 chains 660 201.168|
220 yards
mile (mi)| 8 furlongs {{val|5280}} {{val|1609.344}}|
{{val|1760}} yards or {{val|80}} chains
league (lea)| 3 miles {{val|15840}} {{val|4828.032}}|
No longer an official unit in any nation.{{citation needed|date=June 2017}}
Maritime units
fathom (ftm)| 2.02667 yards 6.0761 {{val|1852}} 1.852|
The British Admiralty in practice used a fathom of 6 feet. This was despite its being {{frac|1000}} of a nautical mile (i.e. 6.08 feet) until the adoption of the international nautical mile.The exact figure was 6.08 feet, but 6 feet was in use in practice. The commonly accepted definition of a fathom was always 6 feet. The conflict was inconsequential, as Admiralty nautical charts designated depths shallower than 5 fathoms in feet on older imperial charts. Today, all charts worldwide are metric, except for USA Hydrographic Office charts, which use feet for all depth ranges.
cable| 100 fathoms 607.61 185.2|
One tenth of a nautical mile. Equal to 100 fathoms under the strict definition.
nautical mile| 10 cables {{val|6076.1}} {{val|1852}}|
Used for measuring distances at sea (and also in aviation) and approximately equal to one arc minute of a great circle. Until the adoption of the international definition of {{val|1852}} metres in 1970, the British nautical (Admiralty) mile was defined as {{val|6080}} feet.The nautical mile was not readily expressible in terms of any of the intermediate units, because it was derived from the circumference of the Earth (like the original metre).
Gunter's survey units (17th century onwards)
link| 7.92 inches {{frac100}} 201.168 {{val|0.201168}}|
{{frac|100}} of a chain and {{frac|{{val|1000}}}} of a furlong
rod| 25 links {{frac4}} {{val|5029.2}} 5.0292|
The rod is also called pole or perch and equal to {{frac|5|1|2}} yards

Area{| class"wikitable" cellspacing3 style"margin-right:0"|+ Area

! Unit! Relation tounits of length! Square feet! Square rods! Square miles! Square metres! Hectares! Notes
Perch (unit of measure)#Area and volume>perch {{nowrap|1 rod × 1 rod}} 272.25 1 {{frac102400}}}} {{val|25.29285264}} {{val|0.002529285264}}|
Although the proper term is square rod, for centuries this unit has been called a pole or perch or, more properly, square pole or square perch.
Rood (unit)>rood {{nowrapACCESSDATE=4 JANUARY 2007 PUBLISHER=NIST ARCHIVEURL=HTTPS://WEB.ARCHIVE.ORG/WEB/20061126120208/HTTP://TS.NIST.GOV/WEIGHTSANDMEASURES/PUBLICATIONS/UPLOAD/H4402_APPENC.PDF, 26 November 2006, {{val|10890}} 40 {{frac2560}}}} {{val|1011.7141056}} {{val|0.10117141056}}|
The rood is {{val|1210}} square yards.
| acre
1 furlong Ã— 1 chain {{val|43560}} 160 {{frac|640}} {{val|4046.8564224}} {{val|0.40468564224}}|
One acre is {{val|4840}} square yards
Note: All equivalences are exact.


In 1824, the various different gallons in use in the British Empire were replaced by the imperial gallon, a unit close in volume to the ale gallon. It was originally defined as the volume of {{convert|10|lb|kg|2}} of distilled water weighed in air with brass weights with the barometer standing at {{convert|30|inHg|0|lk=in}} at a temperature of {{convert|62|°F|°C|0|lk=in}}. In 1963, the gallon was redefined as the volume of 10 pounds of distilled water of density {{val|0.998859|u=g/mL}} weighed in air of density {{val|0.001217|u=g/mL}} against weights of density {{val|8.136|u=g/mL}}, which works out to {{val|4.546092|u=L}}. The Weights and Measures Act of 1985 switched to a gallon of exactly {{val|4.54609|u=L}} (approximately {{val|277.4194|u=cuin}}).ENCYCLOPEDIA,weblink imperial gallon,, 2019-07-10, 25 October 2013, dmy-all, {| class="wikitable" cellspacing=3|+ Table of commonly used volume units! Unit! Imperialounces! Imperialpints! Millilitres! Cubic inches! US ounces! US pints
fluid ounce (fl oz) 1     {{frac|20}}    28.4130625cuin USoz USptsigfig=5|comma=gaps}}
gill (gi) 5     {{frac|4}}    142.0653125cuin USoz USptsigfig=5|comma=gaps}}
pint (pt) 20     1    568.26125cuin USoz USptsigfig=5|comma=gaps}}
quart (qt) 40     2    1136.5225cuin USoz USptsigfig=5|comma=gaps}}
gallon (gal) 160     8    4546.09cuin USoz USptsigfig=5|comma=gaps}}
Note: The millilitre equivalences are exact, but cubic-inch and US measures are correct to 5 significant figures.
{| class="wikitable" cellspacing=3 style="margin-right:0"weblink 13 September 2016, ! Liquid! Dry! Capacity (cu in)
| 8.7
| 17.4
| 34.7
| 69.4
| 138.7

British apothecaries' volume measures

These measurements were in use from 1826, when the new imperial gallon was defined, but were officially abolished in the United Kingdom on 1 January 1971.WEB,weblink The Weights and Measures (Equivalents for dealings with drugs) Regulations 1970, WEB,weblink Museum of the Royal Pharmaceutical Society, London, Information Sheet: 11, In the US, though no longer recommended, the apothecaries' system is still used occasionally in medicine, especially in prescriptions for older medications.BOOK, Zentz, Lorraine C., Math for Pharmacy Technicians,weblink 6 July 2012, 2010, Jones & Bartlett Learning, Sudbury, MA, 978-0-7637-5961-2, 421360709, 7–8, Chapter 1: Fundamentals of Math — Apothecary System,weblink BOOK, Boyer, Mary Jo, Math for Nurses: A Pocket Guide to Dosage Calculation and Drug Preparation,weblink 6 July 2012, 7th, 2009, Wolters Kluwer Health {{pipe, Lippincott Williams & Wilkins |location=Philadelphia, PA |isbn=978-0-7817-6335-6 |oclc=181600928 |pages=108–9 |chapter=UNIT 2 Measurement Systems: The Apothecary System |chapterurl=}}{| class="wikitable" cellspacing=9 style="margin-right:0"group=nb|References for the Table of British apothecaries' volume units: Unit column;BOOK, Royal College of Physicians of Dublin, Royal College of Physicians of Ireland, The Pharmacopœia of the King and Queen's College of Physicians in Ireland,weblink 6 July 2012, 1850, Hodges and Smith, Dublin, 599509441, xlvi, Weights and Measures,weblink National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds. "Appendix C – General Tables of Units of Measurement" (PDF). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. NIST Handbook. 44 (2012 ed.). Washington, D.C.: US Department of Commerce, Technology Administration, National Institute of Standards and Technology. ISSN 0271-4027. OCLC {{OCLC|58927093}}. Retrieved 6 July 2012.{{rp|C-7}}WEB,weblink F, Russ, Rowlett, 13 September 2001, How Many? A Dictionary of Units of Measurement, University of North Carolina at Chapel Hill, Chapel Hill, NC, fluid dram or fluidram (fl dr), 6 July 2012, Symbols & abbreviations column;{{rp|C-5, C-17–C-18}}BOOK, Buchholz, Susan, Henke, Grace, Henke's Med-Math: Dosage Calculation, Preparation and Administration,weblink 6 July 2012, 6th, 2009, Wolters Kluwer Health {{pipe, Lippincott Williams & Wilkins |location=Philadelphia, PA |isbn=978-0-7817-7628-8 |oclc=181600929 |page=55 |chapter=Chapter 3: Metric, Apothecary, and Household Systems of Measurement — Table 3-1: Apothecary Abbreviations |chapterurl=}}BOOK, Pickar, Gloria D., Swart, Beth, Graham, Hope, Swedish, Margaret, Dosage Calculations,weblink 6 July 2012, 2nd Canadian, 2012, Nelson Education, Toronto, 978-0-17-650259-1, 693657704, 528, Appendix B: Apothecary System of Measurement — Apothecary Units of Measurement and Equivalents,weblink Relative to previous column;{{rp|C-7}} Exact metric value column — fluid ounce, pint and gallon,BOOK, United Kingdom, United Kingdom, Department of Trade and Industry, Department of Trade and Industry (United Kingdom), The Units of Measurement Regulations 1995,weblink 1 July 2012, 1995, HMSO, London, 978-0-11-053334-6, 33237616, Schedule: Relevant Imperial Units, Corresponding Metric Units and Metric Equivalents, all other values calculated using value for fluid ounce and the Relative to previous column's values.}}! Unit! Symbols &abbreviations! Relative toprevious! Exactmetric valueThe vinculum over numbers (e.g. {{overline|3}}) represents a repeating decimal.
minim ♏︎, (File:Mx, a symbol for minim in the apothecaries' system.svg|13px), m, m., min   {{gaps8803}}microlitre>µL}}
fluid scruple fl ℈, fl s 20 minims {{gaps8771{{overlineu=mL}}
fluid drachm(fluid dram, fluidram) Ê’, fl Ê’, fÊ’, Æ’ 3, fl dr 3 fluid scruples {{valu=mL}}
fluid ounce â„¥, fl â„¥, fâ„¥, Æ’ â„¥, fl oz 8 fluid drachms {{valu=mL}}
pint O, pt 20 fluid ounces {{valu=mL}}
gallon C, gal 8 pints {{gapsu=L}}
Note: {{Reflist|group=note}}

Mass and weight

In the 19th and 20th centuries, the UK used three different systems for mass and weight. The distinction between mass and weight is not always clearly drawn. Strictly a pound is a unit of mass, although it is commonly referred to as a weight. When a distinction is necessary, the term pound-force may be used to refer to a unit of force rather than mass. The troy pound ({{val|373.2417216|u=g}}) was made the primary unit of mass by the 1824 Act; however, its use was abolished in the UK on 1 January 1879,BOOK, Great Britain, Statutes at large ...,weblink 12 September 2012, 1878, 308, with only the troy ounce ({{val|31.1034768|u=g}}) and its decimal subdivisions retained.BOOK, Chisholm, Hugh, Hugh Chisholm, The Encyclopædia Britannica: A Dictionary of Arts, Sciences, Literature and General Information,weblink 12 September 2012, 1911, At the University Press, 480, The Weights and Measures Act 1855 (18 & 19 Victoria C72) made the avoirdupois pound the primary unit of mass.BOOK, Great Britain, A collection of public general statutes passed in the 18th and 19th years of the reign of Her Majesty Queen Victoria,weblink 5 January 2012, 1855, 273–75, In all the systems, the fundamental unit is the pound, and all other units are defined as fractions or multiples of it.{| class="wikitable" cellspacing=4 style="margin-right:0"|+ Table of mass units! Unit! Pounds! Grams! Kilograms! Notes
grain (gr) {{frac7000}}}} {{val|0.06479891}}64.79891}} milligrams.
drachm (dr) {{frac|256}} {{val|1.7718451953125}}|
ounce (oz) {{frac|16}} {{val|28.349523125}}|
pound (lb) 1 {{val|453.59237}} {{val|0.45359237}}WEBSITE=WWW.LEGISLATION.GOV.UKACCESS-DATE=2019-03-13,
stone (st) 14 {{val|6350.29318}} {{val|6.35029318}}stone is often used when providing a weight (e.g. "this sack weighs 8 stone").DEFINITION OF STONE IN ENGLISH FROM THE OXFORD DICTIONARYWEBSITE = WWW.OXFORDDICTIONARIES.COMACCESSDATE = 2015-11-25, stonedefinition, A person's weight is often quoted in stones and pounds in English-speaking countries that use the avoirdupois system, with the exception of the United States and Canada, where it is usually quoted in pounds.
quarter (qr or qtr) 28 {{val|12.70058636}}qtr}} One quarter is equal to two stones or a quarter of a hundredweight. The term quarter is also used in a retail context to refer to four ounces, a quarter of a pound.
hundredweight (cwt) 112 {{val|50.80234544}}Weights and Measures Act {{Webarchive>url= |date=16 October 2012 }}
ton (t) 2240 {{val|1016.0469088}}2240}} pounds, which is much closer to a metric tonne (about {{val2000kgcomma=gaps}}.
Gravitational units
slug (slug) {{val|32.17404856}} {{val|14593.90294}} {{val|14.59390294}}pound (force)>pound (lbf) is exerted on it.HTTP://WWW.WOLFRAMALPHA.COM/INPUT/?I=SLUG&A=*C.SLUG-_*UNIT->TITLE=WOLFRAM-ALPHA: COMPUTATIONAL KNOWLEDGE ENGINE,
F = ma (Newton's second law)
1 lbf = 1 slug × 1 ft/s2 (as defined above)
1 lbf = 1 lb × standard gravityg/gc (by definition of the pound force{{citation needed>date=October 2017}})
g â‰ˆ {{val|32.17404856}} ft/s2 gc â‰ˆ {{val|32.17404856}} lbm.ft/lbf.s2
1 slug â‰ˆ {{val|32.17404856}} pounds

Natural equivalents

Although the 1824 act defined the yard and pound by reference to the prototype standards, it also defined the values of certain physical constants, to make provision for re-creation of the standards if they were to be damaged. For the yard, the length of a pendulum beating seconds at the latitude of Greenwich at Mean Sea Level in vacuo was defined as {{val|39.01393}} inches. For the pound, the mass of a cubic inch of distilled water at an atmospheric pressure of 30 inches of mercury and a temperature of 62° Fahrenheit was defined as 252.458 grains, with there being 7,000 grains per pound. However, following the destruction of the original prototypes in the 1834 Houses of Parliament fire, it proved impossible to recreate the standards from these definitions, and a new Weights and Measures Act (18 & 19 Victoria. Cap. 72) was passed in 1855 which permitted the recreation of the prototypes from recognized secondary standards.

Relation to other systems

(File:English Length Units Graph.svg|thumb|English units of length)The imperial system is one of many systems of English units. Although most of the units are defined in more than one system, some subsidiary units were used to a much greater extent, or for different purposes, in one area rather than the other. The distinctions between these systems are often not drawn precisely.One such distinction is that between these systems and older British/English units/systems or newer additions. The term imperial should not be applied to English units that were outlawed in the Weights and Measures Act 1824 or earlier, or which had fallen out of use by that time, nor to post-imperial inventions, such as the slug or poundal.The US customary system is historically derived from the English units that were in use at the time of settlement. Because the United States was already independent at the time, these units were unaffected by the introduction of the imperial system.

Current use

missing image!
- MetricImperialUSCustomaryUnits.jpg -
A baby bottle that measures in three measurement systems—metric, imperial (UK), and US customary.

United Kingdom

{{see also|Metrication in the United Kingdom}}British law now{{When|date=September 2019}} defines each imperial unit in terms of the metric equivalent. The metric system is in official use within the United Kingdom for most official applications with Imperial units remaining in widespread use amongst the public.NEWS, Will British people ever think in metric?,weblink 26 February 2017, BBC, 21 December 2011, Jon, Kelly, ...but today the British remain unique in Europe by holding onto imperial weights and measures. ...the persistent British preference for imperial over metric is particularly noteworthy..., All UK roads use the imperial system except for weight limits, and newer height or width restriction signs give metric alongside imperial.NEWS, Height and width road signs to display metric and imperial,weblink 26 February 2017, BBC, 8 November 2014, New road signs showing height and width restrictions will use both metric and imperial measurements from March 2015....Road signs for bridges, tunnels and narrow roads can currently show measurements in just feet and inches or only metres. Some already display both., Units of measurement regulations require all measuring devices used in trade or retail to display measurements in metric quantities. Almost all traders in the UK will accept requests from customers specified in imperial units, and scales which display in both unit systems are commonplace in the retail trade. Metric price signs may be accompanied by imperial price signs provided that the imperial signs are no larger and no more prominent than the metric ones.The United Kingdom completed its official partial transition to the metric system in 1995, with some imperial units still legally mandated for certain applications such as draught beer and cider,WEB,weblinkweblink" title="">weblink 2011-07-20, BusinessLink: Weights and measures: Rules for pubs, restaurants and cafes, 24 August 2009, online, Department for Business, Innovation & Skills, road-signs,WEB,weblink Department for Transport statement on metric road signs, 24 August 2009, 12 July 2002, online, BWMA, and therefore the speedometers on vehicles sold in the UK must be capable of displaying miles per hour. Even though the troy pound was outlawed in the UK in the Weights and Measures Act of 1878, the troy ounce may still be used for the weights of precious stones and metals. The original railways (many built in the Victorian era) are a big user of imperial units, with distances officially measured in miles and yards or miles and chains, and also feet and inches, and speeds are in miles per hour, although more recent systems are metric, and London Underground uses metric.WEB, Facts & Figures,weblink Transport for London, Transport for London, 31 January 2016, Most British people still use imperial units in everyday life for distance (miles, yards, feet and inches) and volume in some cases (especially milk and beer in pints) but rarely for canned or bottled soft drinks or petrol.NEWS, The Guardian, 1 December 2006, In praise of ... metric measurements,weblink London, 29 October 2017, Though use of kilograms is increasing, most British people also still use imperial units in everyday life for body weight (stones and pounds for adults, pounds and ounces for babies).{{Citation needed|date=October 2017}} Some government documents aimed at the public give body weight and height not only in metric units (kilograms centimetres) but also in imperial units (stones and pounds, feet and inches).WEB, BMI healthy weight calculator,weblink National Health Service, 25 November 2015, A survey in 2015 found that many people did not know their body weight or height in one system or the other.WEB, 29 October 2017, 20 June 2015, Will, Dahlgreen,weblink Britain’s metric muddle not changing any time soon, even today [2015] most 18-24 year-olds still do not know how much they weigh in kilograms (60%) or how tall they are in metres and centimetres (54%)., People under the age of 40 preferred the metric system but people aged 40 and over preferred the imperial system.WEB, 29 October 2017, 2015,weblink YouGov Survey Results, The height of horses in some English-speaking countries, including Australia,[1] Canada, the United Kingdom and the United States is usually measured in hands, standardized to 4 inches (101.6 mm). Fuel consumption for vehicles is commonly stated in miles per gallon (mpg), though official figures always include litres per 100 km equivalents. When sold draught in licensed premises, beer and cider must be sold in pints and half-pints. Cow's milk is available in both litre- and pint-based containers in supermarkets and shops. Areas of land associated with farming, forestry and real estate are commonly advertised in acres and square feet, but for official government purposes the units are always hectares and square metres.Office space and industrial units are usually advertised in square feet. Steel pipe sizes are sold in increments of inches, while copper pipe is sold in increments of millimetres. Road bicycles have their frames measured in centimetres, while off-road bicycles have their frames measured in inches. The size (diagonal) of television and computer monitor screens is always denominated in inches. Food sold by length or width e.g. pizzas or sandwiches, is generally sold in inches. Clothing is always sized in inches, with the metric equivalent often shown as a small supplementary indicator. Gas is usually measured by the cubic foot or cubic metre, but is billed like electricity by the kilowatt hour.WEB,weblink Gas meter readings and bill calculation,, Some pre-packaged products show both metric and imperial measures and it is also common to see imperial pack sizes with metric only labels e.g. a {{cvt|1|lb|g|0}} tin of Lyle's Golden Syrup is always labelled 454 g with no imperial indicator. Similarly most jars of jam and packs of sausages are labelled 454 g with no imperial indicator.


India's conversion to the metric system from the imperial system occurred in stages between 1955 and 1962. The metric system in weights and measures was adopted by the Indian Parliament in December 1956 with the Standards of Weights and Measures Act, which took effect beginning 1 October 1958. For the next five years, both the previous and new system were legal. In April 1962, all other systems were banned.WEB,weblinkweblink" title="">weblink dead, 21 February 1999, Metric usage and metrication in other countries, U.S. Metric Association, dmy-all, Today all official measurements are made in the metric system. However, in common usage some older Indians may still refer to imperial units. Some measurements, such as the heights of mountains, are still recorded in feet. Tyre rim diameters are still measured in inches, as used worldwide. Industries like the construction and the real estate industry still use both the metric and the imperial system though it is more common for sizes of homes to be given in square feet and land in acres.Acharya, Anil Kumar. History of Decimalisation Movement in India, Auto-Print & Publicity House, 1958.In Standard Indian English, as in Australian, Singaporean, and British English, metric units such as the litre, metre, and metric tonne utilise the traditional spellings brought over from French, which differ from those used in the United States and the Philippines. The imperial long ton is invariably spelt with one 'n'.

Hong Kong

Hong Kong has three main systems of units of measurement in current use: In 1976 the Hong Kong Government started the conversion to the metric system, and as of 2012 measurements for government purposes, such as road signs, are almost always in metric units. However, all three systems are officially permitted for trade,WEB,weblink CAP 68 WEIGHTS AND MEASURES ORDINANCE Sched 2 UNITS OF MEASUREMENT AND PERMITTED SYMBOLS OR ABBREVIATIONS OF UNITS OF MEASUREMENT LAWFUL FOR USE FOR TRADE, and in the wider society a mixture of all three systems prevails.The Chinese system's most commonly used units for length are (lei5), (zoeng6), (cek3), (cyun3), (fan1) in descending scale order. These units are now rarely used in daily life, the imperial and metric systems being preferred. The imperial equivalents are written with the same basic Chinese characters as the Chinese system. In order to distinguish between the units of the two systems, the units can be prefixed with "Ying" (, jing1) for the Imperial system and "Wa" (, waa4) for the Chinese system. In writing, derived characters are often used, with an additional (mouth) radical to the left of the original Chinese character, for writing imperial units. The most commonly used units are the mile or "li" (, li1), the yard or "ma" (, maa5), the foot or "chek" (, cek3), and the inch or "tsun" (, cyun3).The traditional measure of flat area is the square foot (, fong1 cek3, ping4 fong1 cek3) of the imperial system, which is still in common use for real estate purposes. The measurement of agricultural plots and fields, however, is traditionally conducted in (mau5) of the Chinese system.For the measurement of volume, Hong Kong officially uses the metric system, though the gallon (, gaa1 leon4-2) is also occasionally used.


{{See also|Metrication in Canada}}
missing image!
- GasCan.jpg -
A one US gallon gas can purchased near the US-Canada border. It shows equivalences in imperial gallons and litres.
During the 1970s, the metric system and SI units were introduced in Canada to replace the imperial system. Within the government, efforts to implement the metric system were extensive; almost any agency, institution, or function provided by the government uses SI units exclusively. Imperial units were eliminated from all road signs, although both systems of measurement will still be found on privately owned signs, such as the height warnings at the entrance of a parkade. In the 1980s, momentum to fully convert to the metric system stalled when the government of Brian Mulroney was elected. There was heavy opposition to metrication and as a compromise the government maintains legal definitions for and allows use of imperial units as long as metric units are shown as well.WEB,weblinken#anchorsc:2, Weights and Measures Act: Canadian units of measure, Justice Canada, 14 November 2007, dead, 5 June 2011, dmy-all, WEB
, Guide to Food Labelling and Advertising
, 11
, Canadian Food Inspection Agency
, 1 December 2007
, dead
,weblink" title="">weblink
, 24 January 2008
, dmy
, WEB,weblink Consumer Packaging and Labelling Regulations (C.R.C., c. 417), 15 November 2012, Justice Canada, Legislative Services Branch, The law requires that measured products (such as fuel and meat) be priced in metric units, although an imperial price can be shown if a metric price is present.WEB,weblink A Canadian compromise, 11 March 2008, Canadian Broadcasting Corporation, CBC, Jan 30, 1985,weblink" title="">weblink 2009-01-16, dmy-all, WEB,weblink Les livres et les pieds, toujours présents (eng:The pounds and feet, always present), 11 March 2008, 5 sur 5, Société Radio-Canada, French, However, there tends to be leniency in regards to fruits and vegetables being priced in imperial units only.Environment Canada still offers an imperial unit option beside metric units, even though weather is typically measured and reported in metric units in the Canadian media. However, some radio stations near the United States border (such as CIMX and CIDR) primarily use imperial units to report the weather. Railways in Canada also continue to use Imperial units.Imperial units are still used in ordinary conversation. Today, Canadians typically use a mix of metric and imperial measurements in their daily lives. However, the use of the metric and imperial systems varies by age. The older generation mostly uses the imperial system, while the younger generation more often uses the metric system. {{citation needed |date=July 2019}} Newborns are measured in SI at hospitals, but the birth weight and length is also announced to family and friends in imperial units. Drivers' licences use SI units, though most Canadians give their height and weight in imperial. In livestock auction markets, cattle are sold in dollars per hundredweight (short), whereas hogs are sold in dollars per hundred kilograms. Imperial units still dominate in recipes, construction, house renovation and gardening.WEB,weblink Imperial Measures - The Origins, British Weights and Measures Association,, NEWS,weblink Crepes worth savouring, National Post,, Amy, Rosen, 23 February 2011, NEW,weblink Scoring brownie points, National Post,, Amy, Rosen, 2 February 2011, NEWS,weblink Drinking school, National Post, Adam, McDowell, February 28, 2011, WEB,weblink Home Hardware - Building Supplies - Building Materials - Fence Products, 5 March 2011,weblink" title="">weblink 29 June 2011, dead, dmy-all, Land is now surveyed and registered in metric units, although initial surveys used imperial units. For example, partitioning of farm land on the prairies in the late 19th and early 20th centuries was done in imperial units; this accounts for imperial units of distance and area retaining wide use in the Prairie Provinces. The size of most apartments, condominiums and houses continues to be described in square feet rather than square metres, and carpet or flooring tile is purchased by the square foot. Motor-vehicle fuel consumption is reported in both litres per 100 km and statute miles per imperial gallon,WEB,weblink Fuel Consumption Ratings Search Tool - Conventional Vehicles, Government of Canada, Natural Resources, Canada, leading to the erroneous impression that Canadian vehicles are 20% more fuel-efficient than their apparently identical American counterparts for which fuel economy is reported in statute miles per US gallon (neither country specifies which gallon is used). Canadian railways maintain exclusive use of imperial measurements to describe train length (feet), train height (feet), capacity (tons), speed (mph), and trackage (miles).WEB,weblink Railway Investigation Report R96W0171, Government of Canada, Transportation Safety Board of, Canada, Imperial units also retain common use in firearms and ammunition. Imperial measures are still used in the description of cartridge types, even when the cartridge is of relatively recent invention (e.g., .204 Ruger, .17 HMR, where the calibre is expressed in decimal fractions of an inch). However, ammunition that is already classified in metric is still kept metric (e.g., 9×19mm). In the manufacture of ammunition, bullet and powder weights are expressed in terms of grains for both metric and imperial cartridges.As in most of the western world, air navigation is based on nautical units, e.g., the nautical mile, which is neither imperial nor metric, though altitude is still measured in imperial feetWEB,weblink Canadian Aviation Regulations, Langley Flying School, sec. "Altimeter Rules", in keeping with the international standard.


Metrication in Australia has largely ended the official use of imperial units, though for particular measurements, international use of imperial units is still followed. In licensed venues, draught beer and cider is sold in glasses and jugs with sizes based on the imperial fluid ounce, though rounded to the nearest 5 mL.Australians regularly use imperial units for birth weights, heights and screen sizes.Property size is frequently advertised in acres as well as square metres.Navigation is done in nautical miles, and water-based speed limits are in nautical miles per hour.

New Zealand

Although New Zealand completed metrication in the 1970s, a study of university students undertaken in 1992 found a continued use of imperial units for birth weight and human height alongside metric units."Human use of metric measures of length" {{webarchive |url= |date=9 February 2013 }}. Dignan, J. R. E., & O'Shea, R. P. (1995). New Zealand Journal of Psychology, 24, 21–25.In aviation, altitude and airport elevation are measured in feet whilst navigation is done in nautical miles; all other aspects (fuel quantity, aircraft weight, runway length, etc.) use metric units.Screen sizes for devices such as televisions,WEB,weblink TV buying guide, Noel Leeming, 2018-09-17, monitorsWEB,weblink Shop for Monitor, Computer Monitors, Computer Monitor, Harvey Norman, en, 2018-09-17, and phones,WEB,weblink Mobile Phones, Smartphones {{!, Spark NZ||language=en|access-date=2018-09-17}} and wheel rim sizes for vehicles,WEB,weblink Tyre Sizes {{!, How To Read Your Tyre Size {{!}} Dimensions Explained||language=en|access-date=2018-09-17}} are stated in inches, as is the convention in the rest of the world.


Ireland has officially changed over to the metric system since entering the European Union, with distances on new road signs being metric since 1997 and speed limits being metric since 2005. The imperial system remains in limited use – for sales of beer in pubs (traditionally sold by the pint). All other goods are required by law to be sold in metric units, although old quantities are retained for some goods like butter and sausages, which are sold in 454-gram (1 lb) packaging. The majority of cars sold pre-2005 feature speedometers with miles per hour as the primary unit, but with a kilometres per hour display as well.

Other countries

Some imperial measurements remain in limited use in Malaysia, the Philippines, Sri Lanka and South Africa. Measurements in feet and inches, especially for a person's height, are frequently encountered in conversation and non-governmental publications.Prior to metrication, it was a common practice in Malaysia for people to refer to unnamed locations and small settlements along major roads by referring to how many miles the said locations were from the nearest major town. In some cases, these eventually became the official names of the locations; in other cases, such names have been largely or completely superseded by new names. An example of the former is Batu 32 (literally "Mile 32" in Malay), which refers to the area surrounding the intersection between Federal Route 22 (the Tamparuli-Sandakan highway) and Federal Route 13 (the Sandakan-Tawau highway). The area is so named because it is 32 miles west of Sandakan, the nearest major town.Petrol is still sold by the imperial gallon in Anguilla, Antigua and Barbuda, Belize, Myanmar, the Cayman Islands, Dominica, Grenada, Montserrat, St Kitts and Nevis and St. Vincent and the Grenadines. The United Arab Emirates Cabinet in 2009 issued the Decree No. (270 / 3) specifying that, from 1 January 2010, the new unit sale price for petrol will be the litre and not the gallon. This in line with the UAE Cabinet Decision No. 31 of 2006 on the national system of measurement, which mandates the use of International System of units as a basis for the legal units of measurement in the country.WEB,weblink The Ministry of Agriculture, Government of Grenada, 2004-11-01, Address by Agriculture Minister Gregory Bowen, 15 January 2008, The price of gasoline at the pumps was fixed at EC$7.50 per imperial gallon...,weblink" title="">weblink 24 March 2008, WEB,weblink FAQ,, 15 January 2008, Belize Ministry of Finance,weblink" title="">weblink 2008-01-23, • Kerosene per US Gallon (per Imperial gallon) • Gasoline (Regular)(per imperial Gallon) • Gasoline (Premium) (per Imperial Gallon) • Diesel (per Imperial Gallon), WEB,weblink The High Commission Antigua and Barbuda, 15 January 2008, dead,weblink" title="">weblink 31 January 2009, dmy-all, WEB,weblink International Fuel Prices 2005,, Gerhard P., Metschies, 6 September 2005, 15 January 2008, PDF, 96, German Technical Cooperation,weblink" title="">weblink 2007-02-07, Sierra Leone switched to selling fuel by the litre in May 2011.WEB, Sierra Leone Embassy in the United States,weblink Introduction of the Metric System and the Price of Petroleum Products,weblink" title="">weblink 29 April 2015, 23 October 2011, In October 2011, the Antigua and Barbuda government announced the re-launch of the Metrication Programme in accordance with the Metrology Act 2007, which established the International System of Units as the legal system of units. The Antigua and Barbuda government has committed to a full conversion from the imperial system by the first quarter of 2015.NEWS, Minister Lovell Addresses Metric Conversions,weblink CARIBARENA Antigua, 18 October 2011, 23 October 2011, dead,weblink" title="">weblink 20 October 2011, dmy-all,

See also

{{commons category|British Imperial units}}{{columns-list|colwidth=30em| }}




  • Appendices B and C of weblink" title="">NIST Handbook 44
  • WEB, A., Thompson, Barry N., Taylor,weblink The NIST guide for the use of the international system of units, NIST, 5 October 2010, 15 October 2012, also available as a PDF file,weblink" title="">weblink 16 February 2010, dead, dmy-all,
  • 6 George IV chapter 12, 1825 (statute)

External links

{{systems of measurement}}{{Use dmy dates|date=May 2012}}

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